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Medicine & Surgery Notes

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This is an extract of our Medicine & Surgery document, which we sell as part of our Medicine and Surgery Notes collection written by the top tier of Bristol University students.

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Medicine & Surgery Cardiology Essential anatomy

? Sinus node o Generates impulses automatically by spontaneous depolarisation of its membrane o Pacemaker o Influx of sodium controls the depolarisation

o The rate of depolarisation is controlled by: autonomic tone, stretch, temp, hypoxia, pH
? Atrial & ventricular myocyte action potentials o Different to sinus node cells o Arrival of AP opens Na channels resulting in a fast depolarisation Cardiac Cycle

Cardiac arrhythmias Bradycardia<60bpm Tachycardia>100bpm
? Supraventricular
? Ventricular

Sinus rhythm

Mechanisms of arrhythmia production Sinus bradycardia - slow automacity Bradycadia due to AV block - abnormal conduction in the AV node
? Accelerated automacity o Reducing the threshold potential o Increasing the rate of diastolic depolarization
? Triggered activity o Myocardial damage can lead to oscillations in the transmembrane potential o These 'after depolarisations' may reach the threshold and produce an arrhythmia

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